Recently, patterns formed in microstructures such as semiconductor devices have become increasingly finer. This requires very strict accuracy in the photomask used in the photolithography process for forming such fine patterns.
A technique has been proposed in this context. In this technique, a detection mark formed in the writing region of the photomask is transferred to the light exposure surface of the wafer. By detecting the transferred detection mask, the accuracy of the photomask itself and the accuracy of superposition are inspected.
However, because the detection mark is transferred to the light exposure surface of the wafer, the position for forming the detection mark is significantly restricted.
This results in poor inspection measurement accuracy and makes it difficult to manufacture a photomask with high accuracy.